The channel structure of a mobile radio system for third generation of mobile phones is described for instance in the book by T. Ojanperä, R. Prasad: “Wide Band CDMA for Third Generation Mobil Communication”, Artech House Publishers, 1998, ISBN 0-89006-735-X, in the chapter “6.3.3 Physical Channels” (pp. 169–173). It is described therein that several data channels, referred to as Dedicated Physical Data Channels (DPDCH), and one control or pilot channel, referred to as a Dedicated Physical Control Channel (DPCCH), are available. While the data channels DPDCH are available for transfer of user data, the pilot channel DPCCH is used to transfer a pilot signal. It is proposed in the chapter “5.5.3 Pilot Signals” that pilot signal symbols of the pilot channel DPCCH be used exclusively for synchronization.
However, a disadvantage in using the pilot signal DPCCH for synchronization, which was commonly employed up until now, is that the relative output component of the pilot channel DPCCH is reduced with an increasing activity of the data channel DPDCH, making it difficult to achieve a reliable detection of the correlation peak.
Therefore, there is a need for a reliable determination of the time offset of the CDMA signal.